The “hook and loop” fastener system is a known system providing a releasable coupling between a substrate having hooks and a substrate having loops. Individual loops mate with individual hooks and collectively the system of coupled hooks and loops provide a securing system for two bodies attached to the substrates of hooks and loops. Thermoplastic fastener products having an array of integrally formed, upstanding, engageable fastener hooks can be used with a complementary array of loops (or other complementary fastener elements) to create a system for detachably attaching two surfaces.
One method of producing hooks is to have a sheet of molded stems, and then “coin” a head onto each stem. The coining process involves, generally, applying a heated surface with cavities to the head of each stem, so the top of the head is deformed by one of the cavities to provide a form that can securely mate with a loop on an opposing sheet. One such method is described in U.S. Pat. No. 5,980,230, which issued to Dowd et al. on Nov. 9, 1999.
When coining arrays of mushroom-head hooks for use with complementary loops, it is important that the mushroom heads and stems have similar dimensions and shape. If there are regions having different sizes and shapes of mushroom heads and stems, different regions will provide differing degrees of coupling with a given array of loops in a hook-and-loop detachable attachment system. For example, if a region has mushroom heads which are too small, then for that region there may be only a loose coupling of the loops to the hooks. In contrast, if the heads are too large, then (1) the ease of coupling a hook to a loop decreases and (2) for coupled hooks to loops, it may require more “tearing” force to detach the hook-and-loop parts of the hook-and-loop detachable attachment system.
Such problems are magnified when it is desired to form an array of many small mushroom shaped hooks across a relatively wide hook plate. It is believed that previous methods for molding hooks on a flat surface have only been applied to relatively small work-pieces.